Oil cooling system for supercharged engine

ABSTRACT

In an oil cooling system for a supercharged engine, coolant is introduced from a third coolant supply passage that branches from a first coolant supply passage into a coolant circulation passage of an oil cooler. The coolant has not cooled an engine and a turbocharger. By efficiently cooling lubricating oil (lubricating oil after lubricating supercharger) having lubricated the respective cooled portions of the turbocharger, oil-deterioration-suppressing effect can be improved even with the coolant of a small amount.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2014-120416 filed on Jun. 11, 2014, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an oil cooling system for a supercharged engine which has a supercharger.

BACKGROUND

It is known that a blow-by gas leaking out from a combustion chamber to a crankcase through a gap between a cylinder wall surface and an outer peripheral surface of a piston deteriorates the engine oil (lubricating oil) stored in an oil pan arranged lower than a crankcase.

In order to suppress the oil deterioration, JP-2011-094557A shows a positive crankcase ventilation system in which a fresh air passed through an air cleaner is introduced into the crankcase at a time of supercharging, so as to ventilate the blow-by gas.

JP-2000-199415A shows an oil cooling system for a supercharged engine, which includes an oil supply passage for supplying an lubricating oil from the engine to a supercharger, an oil drain passage for returning the lubricating oil from the supercharger to an oil pan, a first coolant passage for supplying the coolant to the supercharger, and a second coolant passage for discharging the coolant from the supercharger.

In the oil cooling system for a supercharged engine shown in JP-2000-199415A, an oil drain passage where the lubricating oil which has already lubricated the supercharger flows and the second coolant passage where the coolant which has already cooled the supercharger flows are defined by metal pipes. These metal pipes are tightly connected to each other, and thereby the cooling device is constituted. Thus, because the lubricating oil which has lubricated the supercharger is cooled, deterioration of the lubricating oil is suppressed.

However, in the positive crankcase ventilation system shown in JP-2011-094557A, when the operation state of the engine becomes a high load state, the temperature of the housing of the turbo supercharger rises due to the heat receiving from the exhaust gas. The temperature of the lubricating oil which has lubricated the lubricating portion of the turbo supercharger became comparatively high also due to the temperature rise of the housing. The excessively high temperature lubricating oil is easily oxidized and deteriorated.

Further, when the fresh air is introduced into the crankcase, a deterioration of the lubricating oil is promoted by the fresh air.

Although the suppression of lubricating oil deterioration is expected by combining the positive crankcase ventilation system shown in JP-2011-094557A and the oil cooling system shown in JP-2000-199415A, the coolant which has cooled the supercharger is introduced into the supercharger cooling device through the second coolant passage. In other words, the coolant flowing into the supercharger cooling device cools the lubricating oil which has lubricated the supercharger by the coolant. Therefore, the lubricating oil cooling effect was inferior, and the coolant of a large flow rate was required for cooling the lubricating oil so as to secure the oil-deterioration-suppressing effect.

SUMMARY

It is an object of the present disclosure to provide an oil cooling system for a supercharged engine capable of improving the oil-deterioration-suppressing effect even with the coolant of a small amount by utilizing a coolant which has not cooled an internal combustion engine or a supercharger, or a coolant which will not pass through the internal combustion engine or the supercharger.

According to the oil cooling system of the present invention, the lubricating oil which has lubricated a supercharger is cooled by a coolant which has not cooled an internal combustion engine or a supercharger, or a coolant which will not pass the internal combustion engine or the super charger. Therefore, the oil-deterioration-suppressing effect can be improved even with the coolant of a small amount.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a configuration diagram showing a schematic configuration of an oil cooling system for a supercharged engine (first embodiment);

FIG. 2 is a configuration diagram showing a schematic configuration of the oil cooling system for a supercharged engine (first embodiment);

FIG. 3A is a schematic view showing a lubricating oil after lubricating supercharger cooler (first embodiment);

FIG. 3B is a schematic view showing a lubricating oil after lubricating supercharger cooler (first embodiment);

FIG. 4A is a schematic view showing a lubricating oil after lubricating supercharger cooler (first embodiment);

FIG. 4B is a schematic view showing a lubricating oil after lubricating supercharger cooler (first embodiment);

FIG. 5 is a configuration diagram showing a schematic configuration of an oil cooling system for a supercharged engine (second embodiment);

FIG. 6 is a graph showing a relation between the operation time of a supercharged engine and the oil deterioration degree (second embodiment);

FIG. 7 is a configuration diagram showing a schematic configuration of an oil cooling system for a supercharged engine (third embodiment);

FIG. 8 is a configuration diagram showing a schematic configuration of an oil cooling system for a supercharged engine (fourth embodiment);

FIG. 9 is a graph showing a relation between the oil mist amount and the particle size (fourth embodiment);

FIG. 10 is a configuration diagram showing a schematic configuration of a supercharged engine (fourth embodiment);

FIG. 11 is a configuration diagram showing a schematic configuration of an oil cooling system for a supercharged engine (fifth embodiment);

FIG. 12 is a configuration diagram showing a schematic configuration of an oil cooling system for a supercharged engine (sixth embodiment); and

FIG. 13 is a configuration diagram showing a schematic configuration of a supercharged engine (seventh embodiment).

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described in detail based on the drawings.

First Embodiment

FIG. 1 and FIG. 2 show an oil cooling system for a supercharged engine to which an aspect of the present disclosure is applied. FIGS. 3A and 3B and FIGS. 4A and 4B show a first oil cooler 1 which cools a lubricating oil which has lubricated a supercharger. The first oil cooler 1 is incorporated into an oil cooling system for a supercharged engine.

The oil cooling system for a supercharged engine of the present embodiment is applied to a supercharged engine in which a turbocharger T is mounted on an internal combustion engine E. The oil cooling system is provided with an engine lubricating device, an engine cooling device, and the first oil cooler 1. The engine lubricating device is a system that circulates and supplies a lubricating oil (engine oil) to the engine E and the turbocharger T.

The engine cooling device is a system that circulates and supplies a cooling liquid (engine coolant) cooling respective portions of the engine E and respective portions of the turbocharger T.

The first oil cooler 1 is a heat exchanger for cooling the lubricating oil of comparatively high temperature. The lubricating oil receives the exhaust heat from the turbocharger T. The engine coolant cools the lubricating oil in an oil cooling passage between an oil inlet and an oil outlet.

Also, if required, an oil mist separator 2 is installed inside of the oil cooler 1 (refer to FIG. 3A, FIG. 3B, FIG. 4A and FIG. 4B). Further, if required, an oil mist separator 3 is installed outside of the oil cooler 1 (refer to FIG. 8).

The engine E is an engine for an automobile. The engine E includes a plurality of cylinders #1-#4, and employs a multiple cylinder gasoline engine (in-line 4-cylinder engine) that generates output by thermal energy obtained by combusting air fuel mixture of clean air (fresh air) filtered by an air cleaner 4 (refer to FIG. 5) and fuel injected from an injector in a combustion chamber. However, the engine E is not limited to a multiple cylinder gasoline engine, and a multiple cylinder diesel engine may be also applied.

Also, for the engine E, a 4-cycle engine is employed which repeats 4 strokes of an intake stroke, compression stroke, combustion (explosion) stroke, and exhaust stroke.

The engine E includes a cylinder block 5 in which a plurality of cylinders are defined in line, a cylinder head 6 joined to the upper part of the cylinder block 5, and a head cover 7 attached to the upper end of the cylinder head 6. Also, the engine E includes a crankcase 8 provided at a lower part of the cylinder block 5, an oil pan 9 integrally formed in the lower part of the crankcase 8, and a chain case 10 (refer to FIG. 5, FIG. 10 and FIG. 13). The oil pan 9 has an oil storage chamber which stores the lubricating oil therein.

In the cylinder head 6 of the engine E, intake ports 11 and exhaust ports 12 communicating with combustion chambers of the respective cylinders are arranged (refer to FIG. 5). An intake manifold is connected to the intake ports 11 of the respective cylinders. Also, an exhaust manifold is connected to the exhaust ports 12 of the respective cylinders. An intake pipe defining an intake passage is connected to the intake manifold. An air cleaner 4, an intake compressor of the turbocharger T, an intercooler, and an electronic throttle 13 are provided in the intake pipe (refer to FIG. 5).

The intake manifold includes a surge tank that reduces the pressure fluctuation of the intake (supercharged intake) passed through a throttle valve 14 of the electronic throttle 13, and a plurality of intake branch pipes (refer to FIG. 5).

In the plurality of intake branch pipes, a plurality of intake branch passages communicating with the intake ports 11 of the respective cylinders are defined. Also, these intake branch passages are branched to the respective cylinders at each intake branching section arranged upstream end of the intake manifold.

An exhaust pipe defining an exhaust passage is connected to a downstream end of the exhaust manifold. In the exhaust pipe, an exhaust turbine of the turbocharger T, an exhaust purifying device (catalyst), a muffler and the like are installed.

The exhaust manifold includes a plurality of exhaust branch pipes and an exhaust confluent section arranged downstream end of these exhaust branch pipes.

Each branch pipe defines an exhaust branch passages communicating with the intake ports 11 of the respective cylinders. Also, in the downstream section of the exhaust manifold, the exhaust confluent section that gathers the exhaust gas respectively discharged from the respective cylinders is arranged.

Four combustion chambers (cylinder bores) are formed in the cylinder block 5. Inside the respective cylinder bores, pistons 17 connected to a crankshaft 16 through connecting rods 15. In the cylinder block 5 and the cylinder head 6, water jackets (not illustrated) through which the coolant cooling respective cooled portions of the engine E circulates are arranged.

In the cylinder head 6, at least one intake ports 11 independently connecting with the combustion chamber of one cylinder are arranged. At the intake ports 11 of the respective cylinders, intake valves 18 that respectively open/close the intake port openings of the respective cylinders are installed.

Also, in the cylinder head 6, at least one exhaust ports 12 that independently connect with the combustion chamber of one cylinder are arranged. At the exhaust ports 12 of the respective cylinders, exhaust valves 19 that respectively open/close exhaust port openings of the respective cylinders are installed.

The intake valves 18 are configured so that the opening/closing motion thereof is controlled by intake cams 22 arranged on an intake camshaft 21 rotatably supported on the cylinder head 6 corresponding to the intake valves 18 of the respective cylinders (refer to FIG. 5).

On the other hand, the exhaust valves 19 are configured so that the opening/closing motion thereof is controlled by exhaust cams 24 arranged on an exhaust camshaft 23 rotatably supported on the cylinder head 6 corresponding to the exhaust valves 19 of the respective cylinders (refer to FIG. 5).

The intake and exhaust camshafts 21, 23 rotate in a fixed direction synchronizing with the crankshaft 16 of the engine E. These intake and exhaust camshafts 21, 23 are synchronously driven with the crankshaft 16 so as to rotate once as the crankshaft 16 rotates twice.

Also, to the cylinder head 6, a plurality of spark plugs igniting the air fuel mixture having flown into the combustion chambers of the respective cylinders and a plurality of injectors (fuel injection valves of an in-port injecting type) injecting the fuel to the intake ports 11 of the respective cylinders are attached. Further, in the case of an injector (fuel injection valve) of an in-cylinder directly injecting type, fuel is injected to the intake having flown into the combustion chambers of the respective cylinders.

The intercooler is a heat exchanger for cooling supercharged intake air (supercharged air, compressed air) with the coolant (or cooling air) which is a cooling medium and cools the supercharged intake. The outlet end of the intercooler is connected to the throttle body of the electronic throttle 13 through the intake pipe.

Also, as the respective cooled portions of the turbocharger T, the cooler core (heat exchanging section) or the heat exchanger tube of the intercooler may also be used.

The electronic throttle 13 includes a throttle body that constitutes a part of the intake pipe, a throttle valve 14 rotatably stored in the inside of the throttle body and adjusting (regulating) the flow rate of the intake fed from the intake compressor to the respective cylinders of the engine E, an electric actuator (not illustrated) opening/closing the throttle valve 14, and a throttle opening sensor (not illustrated) outputting a signal corresponding to the opening of the throttle valve 14 (throttle opening) to an engine control device (electronic control unit: ECU).

Also, the electric actuator has a throttle motor (electric motor) generating the power torque to rotationally drive the throttle valve 14 when electric power is received, a speed reducing mechanism reducing the speed of rotation of an output shaft of the throttle motor and transmitting the same to a rotary shaft of the throttle valve 14, and the like.

In the engine E, a blow-by gas ventilation device is arranged which recirculates the blow-by gas to the intake passage of the engine E. The blow-by gas flows out into the crankcase 8 from the gap between the cylinder wall surface of the cylinder block 5 and the outer peripheral surface of the piston 17.

The blow-by gas ventilation device is configured to draw out the blow-by gas generated in the inside (crank chamber 25) of the crankcase 8, to recirculate the same to the intake passage of the engine E, to re-combust the same in the respective cylinders of the engine E, to introduce fresh air filtered by the air cleaner 4 to the crankcase 8, and to ventilate the inside of the crank chamber 25.

The intake passage of the engine E includes a first intake passage 31 introducing the intake air passed through the air cleaner 4 to the intake compressor of the turbocharger T, a second intake passage 32 introducing the intake air compressed by the intake compressor to the throttle valve 14 of the electronic throttle 13, and a third intake passage 33 supplying the intake air of which flow rate is adjusted by the throttle valve 14 to the respective cylinders and the intake ports 11 of the engine E (refer to FIG. 5).

The first intake passage 31 communicates with the outside (atmospheric air) through an outside air introduction port of the air cleaner 4.

The second intake passage 32 communicates with the first intake passage 31 through the intake passage inside the intake compressor of the turbocharger T.

The third intake passage 33 communicates with the second intake passage 32 through the intake passage (throttle bore) inside the throttle body of the electronic throttle 13.

The blow-by gas ventilation device includes a fresh air introduction passage 34 and a blow-by gas reduction passage 35 for preventing sucking-up of the lubricating oil (refer to FIG. 5).

The fresh air introduction passage 34 connects the first intake passage 31) and a valve gear chamber 27. The valve gear chamber 27 is defined between the cylinder head 6 and the head cover 7 and communicates with the crank chamber 25 through a connecting passage 26 (refer to FIG. 5).

The blow-by gas reduction passage 35 connects the crank chamber 25 to the third intake passage 33.

The turbocharger T includes the intake compressor (an impellor 41, a housing 42) arranged in the middle of the intake pipe through which the intake flows from the air cleaner 4 to the throttle body and the surge tank of the intake manifold, and an exhaust turbine (an impellor 43, a housing 44, a shaft 45) arranged in the middle of the exhaust pipe through which the exhaust flows from the exhaust gathering section of the exhaust manifold to the catalyst. In the turbocharger T, a center housing 46 is installed between the housing 42 of the intake compressor and the housing 44 of the exhaust turbine.

When the impellor 43 is rotationally driven by exhaust energy (exhaust pressure), the shaft 45 and the impellor 41 also rotate, and the impellor 41 compresses the intake air and feeds the same into the combustion chambers of the engine E.

The intake compressor includes the impellor (compressor impellor) 41 rotatable around the rotation axis of the shaft 45, and the housing (compressor housing) 42 installed so as to surround the periphery of the impellor 41. The housing 42 is formed of metal or synthetic resin.

The housing 44 of the exhaust turbine and the center housing 46 are formed of a heat resistant metal (for example a heat resistant aluminum alloy, a heat resistant steel, and the like). Also, in the housing 44 and the center housing 46, water jackets W1, W2 through which the coolant cooling the turbocharger T circulates are formed.

In the center housing 46, first and second bearing holes extending in the rotation axis direction of the shaft 45 are formed. Inside these first and second bearing holes, first and second radial bearings 47 are held respectively.

In the turbocharger T of the present embodiment, the shaft 45 is rotatably supported by the bearings 47 in a bearing storage chamber 48. Also, the bearing storage chamber 48 is separated into an intake bearing storing chamber and an exhaust bearing storing chamber by a seal member.

In the center housing 46, an oil supply section is arranged which supplies lubricating oil from an oil pump to the bearing storage chamber 48.

The oil supply section includes an oil pouring port 51, an oil introduction passage (oil supply passage) 52 to which the lubricating oil is introduced from the oil pouring port 51, an oil distribution passage (oil supply passage) 53 that distributes and supplies the lubricating oil from the oil introduction passage 52 to the respective bearings 47, and an oil discharge port 54 for discharging the lubricating oil from the bearing storage chamber 48 toward the oil pan 9.

Next, the detail of an engine lubricating device of the present embodiment will be described briefly based on FIG. 1 to FIG. 4.

The engine lubricating device includes an oil circulation passage that circulates and supplies the lubricating oil stored in the oil pan 9 to the turbocharger T and the engine E. An oil pump 55 generates a circulation flow of the lubricating oil in the oil circulation passage, and a second oil cooler 56 for cooling the lubricating oil which has not lubricated the engine E by utilizing the coolant.

The oil pump 55 is attached to the cylinder block 5 of the engine E. This oil pump 55 is rotationally driven synchronizing with the rotation of the crankshaft 16 of the engine E, and forcibly circulates the lubricating oil into the oil circulation passage. This oil pump 55 sucks the lubricating oil stored in the oil pan 9, pressurizes the lubricating oil and discharges the same to the oil circulation passage side.

The second oil cooler 56 is attached to the cylinder block 5 of the engine E. The second oil cooler 56 includes an inner pipe and an outer pipe arranged so as to cover the outer periphery of the inner pipe. A coolant circulation passage is formed between the outer periphery of the inner pipe and the outer pipe.

At the upstream end of the inner pipe, an oil introduction pipe is arranged which introduces the lubricating oil from the engine E into the oil cooling passage. Also, at the downstream end of the inner pipe, an oil lead-out pipe is arranged which leads-out the lubricating oil from the oil cooling passage into the oil pan 9.

At the upstream end of the outer pipe, a coolant introduction pipe is arranged which introduces the coolant from a radiator 57 and a water pump 58 into the coolant circulation passage. Also, at the downstream end of the outer pipe, a coolant lead-out pipe is arranged which leads out the coolant from the coolant circulation passage to the engine E or the radiator 57.

Further, inner fins improving the heat exchange performance may be installed in the oil cooling passage or the coolant circulation passage.

The second oil cooler 56 is a heat exchanger for cooling lubricating oil which circulates through the oil circulation passage.

The second oil cooler 56 cools the lubricating oil so that the lubricating oil temperature falls within a predetermined temperature range (for example 60-80° C.). Thus, by circulating and supplying the lubricating oil to the turbocharger T and the engine E, the lubricating portions of the turbocharger T and the lubricating portions of the engine E are effectively cooled and lubricated.

The oil circulation passage includes an oil supply passage that supplies the lubricating oil to the engine E and the turbocharger T, and an oil discharge passage that returns lubricating oil (lubricating oil after lubricating supercharger) having lubricated the respective lubricating portions of the turbocharger T and lubricating oil (lubricating oil after lubricating internal combustion engine) having lubricated the respective lubricating portions of the engine E to the inside of the oil storage chamber of the oil pan 9 of the engine E.

The oil supply passage includes a first oil supply passage 59 that supplies lubricating oil to the turbocharger T, a second oil supply passage 60 that supplies lubricating oil to the engine E (refer to FIG. 1 and FIG. 2).

In the turbocharger T, the sliding section between the shaft 45 and the two bearings 47 is lubricated.

Also, in the engine E, the sliding section between respective cylinder wall surfaces of the cylinder block 5 and the outer peripheral surfaces of the respective pistons 17, the intake valve gear mechanism between the intake cam 22 and the intake valves 18, the exhaust valve gear mechanism between the exhaust cams 24 and the exhaust valves 19 (refer to FIG. 5) are lubricated.

The oil discharge passage includes a first oil discharge passage 61 that leads the lubricating oil into the oil cooling passage of the first oil cooler 1, a second oil discharge passage 62 that leads the lubricating oil into the oil pan 9, a third oil discharge passage 63 that leads lubricating oil into the oil cooling passage of the second oil cooler 56, a fourth oil discharge passage 64 that leads the lubricating oil into the oil pan 9 (refer to FIG. 1 and FIG. 2).

The first oil discharge passage 61 is connected to the first oil supply passage 59 through the turbocharger T.

The second oil discharge passage 62 is connected to the first oil discharge passage 61 through the oil cooling passage of the first oil cooler 1.

The third oil discharge passage 63 is connected to the second oil supply passage 60 through the engine E.

The fourth oil discharge passage 64 is connected to the third oil discharge passage 63 through the oil cooling passage of the second oil cooler 56.

Next, the detail of the engine cooling device will be described briefly based on FIG. 1.

The engine cooling device includes the radiator 57, a coolant circulation passage (circuit) that circulates and supplies the coolant to the engine E and the turbocharger T, and the water pump 58 that generates a circulation flow of the coolant in the coolant circulation passage.

The engine E has portions exposed to the combustion heat and exhaust heat out of the cylinder block 5 and the cylinder head 6. In the engine E, water jackets are arranged through which the coolant is circulated. The water jackets are arranged so as to surround the periphery of the cylinder bores of the respective cylinders and the periphery of the exhaust ports 12 of the respective cylinders.

Also, the turbocharger T has portions exposed to the exhaust heat out of the housing 44 and the center housing 46. In the turbocharger T, water jackets W1, W2 are arranged through which the coolant cooling the housing 44 and the center housing 46 are circulated. The water jackets W1, W2 are arranged so as to surround the periphery of the exhaust passage through which the exhaust gas circulates.

The radiator 57 is a heat exchanger that cools the coolant sucked by the water pump 58.

The radiator 57 includes a plurality of tubes through which the coolant circulates, an upper head tank connected to the tubes and a lower head tank connected to the tubes.

The radiator 57 cools the coolant circulating through the coolant circulation passage to a predetermined temperature range (for example 60-80° C.) by heat-exchanging. The coolant of the predetermined temperature range is circulated and supplied to the water jackets of the engine E, the water jackets W1, W2 of the turbocharger T and the first oil cooler 1.

The water pump 58 is attached to the cylinder block 5 of the engine E. The water pump 58 is a coolant pump that generates a circulation flow of the coolant in the coolant circulation passage. The water pump 58 sucks the coolant cooled by the radiator 57, pressurizes the sucked coolant and feeds the same to the coolant circulation passage.

The coolant circulation passage includes a coolant supply passage that supplies the coolant discharged from the water pump 58 to the engine E and the turbocharger T, and a coolant discharge passage that returns the coolant to the upper head tank of the radiator 57.

The coolant supply passage includes first and second coolant passages. The first coolant passage includes a first coolant supply passage 71 that supplies the coolant from the water pump 58 to the engine E, and a second coolant supply passage 72 that supplies the coolant from the water pump 58 to the turbocharger T. The second coolant passage includes a third coolant supply passage 73 that supplies the coolant from the water pump 58 to the first oil cooler 1.

The first coolant supply passage 71 connects the water pump 58 to the engine E.

The second coolant supply passage 72 branches from a first branch section 71 a of the first coolant supply passage 71 and connects the first branch section 71 a to the turbocharger T.

The third coolant supply passage 73 branches from a second branch section 71 b of the first coolant supply passage 71 and connects the second branch section 71 b to the coolant circulation passage of the first oil cooler 1. The third coolant supply passage 73 is separated from the second coolant supply passage 72, and is connected to the second coolant supply passage 72 in parallel.

The coolant discharge passage includes a first coolant discharge passage 74 that returns the coolant from the engine E to the upper head tank of the radiator 57, a second coolant discharge passage 75 that returns the coolant from the turbocharger T to the upper head tank of the radiator 57, and a third coolant discharge passage 76 that returns the coolant from the oil cooling passage of the first oil cooler 1 to the upper tank of the radiator 57.

The first coolant discharge passage 74 is connected to the first coolant supply passage 71 through the engine E.

The second coolant discharge passage 75 joins the first coolant discharge passage 74 at a first joining section 74 a located upstream of the radiator 57, and connects the turbocharger T to the first joining section 74 a.

The third coolant discharge passage 76 joins the first coolant discharge passage 74 at a second joining section 74 b located upstream of the radiator 57 and downstream of the first joining section 74 a. The third coolant discharge passage 76 connects the coolant circulation passage of the first oil cooler 1 to the second joining section 74 b.

The detail of the first oil cooler 1 will be described based on FIG. 1 to FIG. 4B.

The first oil cooler 1 is a heat exchanger for cooling the lubricating oil which has lubricated the turbocharger T by utilizing the coolant discharged from the water pump 58.

The first oil cooler 1 includes an inner pipe 81 defining an oil cooling passage 68, and an outer pipe 82 arranged around the outer peripheral of the inner pipe 81. A coolant circulation passage 78 is defined between the outer periphery of the inner pipe 81 and the outer pipe 82.

At the upstream end of the inner pipe 81, an oil introduction pipe 67 is arranged which introduces the lubricating oil from the first oil discharge passage 61 into the oil cooling passage 68. Also, at the downstream end of the inner pipe 81, an oil lead-out pipe 69 is arranged which leads out the oil from the oil cooling passage 68 into the oil pan 9 through the second oil discharge passage 62.

The oil introduction pipe 67 is connected to an oil inlet section at the upstream end of the oil cooling passage 68 of the first oil cooler 1. Also, the oil lead-out pipe 69 is connected to an oil outlet section at the downstream end of the oil cooling passage 68 of the first oil cooler 1.

Further, inner fins improving the heat exchange performance may be installed in the oil cooling passage 68.

At the upstream end of the outer pipe 82, a coolant introduction pipe 77 is arranged which introduces the coolant from the third coolant supply passage 73 into the coolant circulation passage 78. Also, at the downstream end of the outer pipe 82, a coolant lead-out pipe 79 is arranged which leads out the coolant from the coolant circulation passage 78 to the upper head tank of the radiator 57 through the third coolant discharge passage 76 and the first coolant discharge passage 74.

The coolant introduction pipe 77 is connected to the coolant inlet section at the upstream end of the coolant circulation passage 78 of the first oil cooler 1. Also, the coolant lead-out pipe 79 is connected to the coolant outlet section at the downstream end of the coolant circulation passage 78 of the first oil cooler 1.

Further, inner fins improving the heat exchange performance may be installed in the coolant circulation passage 78.

Also, the first oil cooler 1 is configured to cool the lubricating oil utilizing the coolant by a convectional flow in which the lubricating oil flows from one side to the other side of the oil cooler 1, and the coolant flows from the other side to one side of the first oil cooler 1.

While the engine is operated, particularly when the engine E is in a heavy load state, majority of the lubricating oil after lubricating turbocharger T becomes oil mist of a high temperature. The oil mist flows into the first oil discharge passage 61. Since the oil mist is at a high temperature and in a state of having large surface area, oxidation and deterioration of the lubricating oil stored in the oil pan 9 are promoted when the oil mist returns into the oil pan 9 of the engine E.

More specifically, because the inside temperature of the bearing storage chamber 48 of the turbocharger T is comparatively high, the lubricating oil is liable to become a mist form. Also, when the particle size of the mist becomes small, the surface area increases and the reaction with oxygen becomes quick, and therefore deterioration of the lubricating oil is promoted. Accordingly, it is necessary to cool and liquefy the oil mist to separate from the air.

Therefore, in the present embodiment, as shown in FIG. 3A, in the oil cooling passage 68 inside of the first oil cooler 1, the oil mist separator 2 for separating the oil mist and the air is installed. Thus, in the first oil cooler 1 of the present embodiment, because the lubricating oil returns into the oil pan 9 after liquefied by the oil mist separator 2, the oil-deterioration-suppressing effect can be secured.

The oil cooler 1 includes the oil cooling passage 68, the coolant circulation passage 78 and the oil mist separator 2. The oil cooling passage 68 is connected between the first and second oil discharge passages 61, 62. The lubricating oil is cooled by utilizing the coolant introduced from the third coolant supply passage 73 into the coolant circulation passage 78. The oil mist separator 2 captures the oil mist in the oil cooling passage 68.

As shown in FIG. 3B, the oil mist separator 2 has an oil mist filter 83 that gathers and liquefies the oil mist in the air, and separates the oil mist (liquid component) and the air (gas component) from each other.

Also, as shown in FIG. 4A, the oil mist separator 2 may have a plurality of collision plates 84 which project into the oil cooling passage 68 so as to thermally contact the lubricating oil which has lubricated the turbocharger T. These collision plates 84 are formed integrally on the inner peripheral surface of the inner pipe 81. Also, the collision plates 84 project from the inner wall surfaces of the inner pipe 81 to the oil cooling passage 68. The collision plates 84 are disposed alternately along the flow direction of the lubricating oil.

Also, as shown in FIG. 4B, the oil mist separator 2 may have a plurality of collision plates 85 in addition to the collision plates 84 described above. The collision plates 85 projects from an outer wall surface of the inner pipe 81 to the coolant circulation passage 78.

Also, the collision plates 84, 85 are mutually continuously connected to each other, and are formed integrally on the inner peripheral surface and the outer peripheral surface of the inner pipe 81.

In this case, the projecting ends of the collision plates 84 project into the oil cooling passage 68, the projecting ends of the collision plates 85 project into the coolant circulation passage 78, and therefore the heat received from the lubricating oil can be efficiently radiated to the coolant. Thus, an effect as the inner fins improving the heat exchange efficiency of the lubricating oil and coolant can be secured, and the lubricating oil after lubricating supercharger can be cooled more efficiently.

As described above, the oil mist separator 2 installed in the inside of the oil cooler 1 may be the oil mist filter 83 or collision plates 84, 85. In order that the first and second oil discharge passages 61, 62 and the oil cooling passage 68 are not clogged with the lubricating oil, it is necessary to sufficiently reduce the pressure loss of the lubricating oil that circulates through the first and second oil discharge passages 61, 62 and the oil cooling passage 68.

Operation of First Embodiment

The operation of the oil cooling system of the present embodiment will be described based on FIG. 1.

When operation of the engine E is started, the oil pump 55 rotationally driven by the crankshaft 16 of the engine E operates to pump up the lubricating oil stored in the oil storage of the oil pan 9.

Then, the lubricating oil discharged from the oil pump 55 is distributed and supplied to the turbocharger T and the engine E through the first oil supply passage 59 or the second oil supply passage 60.

The lubricating oil introduced into the oil introduction passage 52 is distributed by the oil distribution passage 53 to the intake bearing storage chamber and the exhaust bearing storage chamber of the bearing storage chamber 48. The respective bearings 47 are lubricated by the lubricating oil supplied from the first oil supply passage 59. Then, the lubricating oil is led out from the oil discharge port 54 into the first oil discharge passage 61.

The lubricating oil led out from the oil discharge port 54 flows through the first oil discharge passage 61 toward the oil cooling passage 68 of the oil cooler 1. The lubricating oil is thereafter led out from the oil cooling passage 68 into the second oil discharge passage 62. Then, the lubricating oil led out from the oil cooler 1 flows through the second oil discharge passage 62, and is returned into the oil storage chamber of the oil pan 9 of the engine E.

The water pump 58 circulates the coolant cooled by the radiator 57 through the coolant circulation passage. Because the water pump 58 also operates during operation of the engine E, the coolant discharged from water pump 58 is circulated and supplied into the water jackets of the engine E through the first coolant supply passage 71.

Then, the coolant introduced into the water jackets of the engine E cools the engine E (for example, the cylinder block 5 and the cylinder head 6 exposed to the combustion heat and exhaust heat). Then, the coolant is introduced into the first coolant discharge passage 74. Further, the coolant flowing through the first coolant discharge passage 74 is introduced into the radiator 57 and the water pump 58.

The second coolant supply passage 72 branches from the first branch section 71 a in the middle of the first coolant supply passage 71, and the second coolant discharge passage 75 joins the first coolant discharge passage 74 at the first joining section 74 a.

The coolant introduced into the second coolant supply passage 72 passes through the second coolant supply passage 72, and is circulated and supplied into the water jackets W1, W2 of the turbocharger T for cooling the turbocharger T.

The coolant introduced into the water jackets W1, W2 of the turbocharger T cools the respective portions of the turbocharger T (for example, the housing 44 and the center housing 46 exposed to the exhaust heat), and is thereafter led out from the water jacket W2 of the turbocharger T into the second coolant discharge passage 75.

The coolant led out from the turbocharger T passes through the second coolant discharge passage 75 and joins the coolant flowing through the first coolant discharge passage 74 at the first joining section 74 a. The coolant is thereafter introduced to the radiator 57 and the water pump 58.

The third coolant supply passage 73 branches from the second branch section 71 b of the first coolant supply passage 71. The third coolant discharge passage 76 joins the first coolant discharge passage 74 at the second joining section 74 b.

The coolant introduced from the first coolant supply passage 71 into the third coolant supply passage 73 passes through the third coolant supply passage 73, and is circulated and supplied into the coolant circulation passage 78 of the first oil cooler 1 for cooling the lubricating oil which has lubricated the turbocharger T.

The coolant introduced into the coolant circulation passage 78 of the oil cooler 1 cools the lubricating oil which circulates through the oil cooling passage 68 of the first oil cooler 1, and is thereafter led out from the oil cooling passage 68 of the oil cooler 1 into the third coolant discharge passage 76.

The coolant led out from the coolant circulation passage 78 of the oil cooler 1 passes through the third coolant discharge passage 76, and joins the coolant flowing through the first coolant discharge passage 74 at the second joining section 74 b. Thereafter, the coolant is introduced to the radiator 57 and the water pump 58.

Effect of First Embodiment

By efficiently cooling the lubricating oil which has lubricated the turbocharger T by utilizing the coolant which has not passed through the engine E and the turbocharger T, the oil-deterioration-suppressing effect can be improved even with the coolant of a small amount.

In the oil cooling system shown in JP-2000-199415A, it is configured that the coolant which has cooled the turbo supercharger is introduced from the second coolant supply passage to the oil cooler. However, in the oil cooling system of the present embodiment, the coolant introduced to the oil cooler 1 has not cooled the high temperature sections such as the housing 44 and the center housing 46 of the turbocharger T. Therefore, the coolant temperature becomes lower than that of conventional oil cooling systems.

Also, because the oil cooler 1 is located downstream of the water pump 58, even when the shape of the coolant circulation passage 78 of the first oil cooler 1 is made complicated with a large pressure loss, the pressure in the coolant circulation passage 78 of the first oil cooler 1 becomes positive pressure, so that no cavitation occurs. Thus, a complicated shape such as a fin shape can be employed.

Furthermore, a more efficient oil cooler 1 can be achieved which cools the lubricating oil utilizing the coolant by a convectional flow in which the lubricating oil flows from one side to the other side of the oil cooler 1, and the coolant flows from the other side to one side of the oil cooler 1.

As described above, in the oil cooling system for a supercharged engine of the present embodiment, the temperature of the coolant circulated and supplied to the coolant circulation passage 78 of the oil cooler 1 can be lowered, and the oil cooler 1 can have a structure having excellent cooling efficiency. Therefore, the temperature of the oil after lubricating supercharger can be lowered, and the coolant amount can be reduced.

Also, the first oil cooler 1 can be individually installed for cooling the lubricating oil after lubricating a supercharger. It is also possible to integrate the second oil cooler 56 and the first oil cooler 1 as shown in FIG. 2 so that increase of the number of pieces of components can be suppressed.

While the engine is operated, particularly when the engine operation condition is under a heavy load, majority of the lubricating oil after lubricating supercharger becomes oil mist of a high temperature by the heat of the exhaust gas. In the first oil cooler 1 shown in FIGS. 3A to 4B, after the oil mist is liquefied by the oil mist separator, the lubricating oil is returned to the oil pan 9. Therefore the oil-deterioration-suppressing effect can be improved.

Second Embodiment

FIG. 5 and FIG. 6 show an oil cooling system for a supercharged engine according to a second embodiment.

The reference signs same as those of the first embodiment show the same configuration or function, and description thereof will be omitted.

The oil cooling system for a supercharged engine of the present embodiment is applied to a supercharged engine in which a turbocharger T is mounted on an engine E for a vehicle, and includes a supercharged engine lubricating device that circulates and supplies lubricating oil for lubricating the engine E and the turbocharger T. An engine cooling device circulates and supplies coolant to the engine E and the turbocharger T. The first oil cooler 1 cools the lubricating oil which has lubricated the supercharger by heat exchanging. The first to third intake passages 31 to 33 supply intake air passed through the air cleaner 4 into the combustion chambers through the intake compressor of the turbocharger T, the intercooler, the throttle valve 14 of the electronic throttle 13, the surge tank, the intake manifold, and the intake port 11 of the cylinder head 6.

Conventionally, for suppressing deterioration of lubricating oil, the fresh air passed through the air cleaner 4 is introduced from the fresh air introduction passage 34 to the crankcase 8 so as to ventilate the inside of the crank chamber 25. However, in the supercharged engine in which the turbo supercharger T is mounted on the engine E, the lubricating oil after lubricating supercharger becomes high temperature and reacts with oxygen in the fresh air. It is likely that deterioration of the lubricating oil may proceed.

Therefore, it is necessary to improve the lubricating oil-deterioration-suppressing effect by combining the first embodiment and a crankcase ventilation system.

The crankcase ventilation system includes the fresh air introduction passage 34 branching from the first intake passage 31 that introduces the fresh air passed through the air cleaner 4 into the housing 42 of the intake compressor of the turbo supercharger T. This fresh air introduction passage 34 connects the air cleaner 4 to the valve gear chamber 27 of the engine E.

Also, the valve gear chamber 27 is formed between the cylinder head 6 and the head cover 7 of the engine E. The intake valve gear mechanism opens/closes the intake valves 18 of the respective cylinders. The exhaust valve gear mechanism opens/closes the exhaust valves 19 of the respective cylinders.

Also, the crankcase ventilation system includes the blow-by gas reduction passage 35 that connects the valve gear chamber 27 that communicates with the inside (the crank chamber 25) of the crankcase 8 through the connecting passage 26 to the intake passage (the third intake passage 33) on the downstream side of the throttle valve 14 of the electronic throttle 13 in the flow direction of the intake each other, and a check valve 36 that is installed in the middle of this negative pressure time blow-by gas reduction passage 35 and prevents back flow of the blow-by gas from the third intake passage 33 side toward the valve gear chamber 27.

The negative pressure time blow-by gas reduction passage 35 is a passage for recirculating the blow-by gas from the valve gear chamber 27 to the third intake passage 33.

Also, the crankcase ventilation system includes a second blow-by gas reduction passage 37 and the negative pressure generating device 38.

In the present embodiment, as the negative pressure generating device 38, an electric pump, a mechanical pump, negative pressure of supercharger, and the like are utilized.

When the engine E is operated in a low load state, the pressure of the third intake passage 33 downstream of the throttle valve 14 becomes negative pressure. At this time, the check valve 36 is opened by the pressure difference between the front and back thereof.

Thus, the blow-by gas is sucked from the valve gear chamber 27 through the blow-by gas reduction passage 35. Then, the blow-by gas is discharged into the intake air that flows through the third intake passage 33.

The fresh air passed through the air cleaner 4 is led from the first intake passage 31 into the valve gear chamber 27 through the fresh air introduction passage 34. Thereafter, the fresh air is led from the valve gear chamber 27 to the crank chamber 25 of the crankcase 8 through the connecting passage 26. Thus, the blow-by gas can be recirculated to the intake system of the engine E, and the fresh air passed through the air cleaner 4 can be introduced into the crank chamber 25 of the crankcase 8 to ventilate the crank chamber 25.

Also, when the engine E is operated in a high load state and the pressure of the third intake passage 33 becomes positive pressure, the negative pressure is generated in the second blow-by gas reduction passage 37 by operating the negative pressure generating device 38. At this time, the check valve 36 is closed by the pressure difference between the front and back thereof.

Thus, the blow-by gas is sucked from the valve gear chamber 27 through the second blow-by gas reduction passage 37 by the negative pressure generated by the negative pressure generating device 38. Then, the sucked blow-by gas is discharged into the intake air that flows through the first intake passage 31.

The fresh air passed through the air cleaner 4 is led from the first intake passage 31 into the valve gear chamber 27 through the fresh air introduction passage 34. Then, the fresh air is led from the valve gear chamber 27 to the crank chamber 25 of the crankcase 8 through the connecting passage 26. Thus, the blow-by gas can be recirculated to the intake system of the engine E, and the blow-by gas in the crank chamber 25 of the crankcase 8 can be ventilated.

Also, since the check valve 36 is in a closed state during the supercharging of the engine E, the back flow in the blow-by gas reduction passage 35 can be prevented.

Further, because the second blow-by gas reduction passage 37 is connected to the fresh air introduction passage 34 of the first intake passage 31, the blow-by gas sucked from the second blow-by gas reduction passage 37 into the first intake passage 31 can be prevented from being mixed with the fresh air introduced from the first intake passage 31 to the fresh air introduction passage 34.

In FIG. 6, the references “▪” show a case where the ventilation and the cooling of the lubricating oil are performed. The references “⋄” show a case where only the ventilation by negative pressure is performed. The references “□” shows a case where the ventilation by the negative pressure and the supercharging pressure is performed.

Therefore, the blow-by gas generated in the crankcase 8 can be recirculated to the intake passage of the engine E, and the clean fresh air passed through the air cleaner 4 can be introduced into the crankcase 8 to ventilate the crank chamber 25.

As described above, the oil cooling system for a supercharged engine of the present embodiment exerts effects similar to those of the first embodiment.

Third Embodiment

FIG. 7 shows an oil cooling system for a supercharged engine according to a third embodiment.

The reference signs same as those of the first and second embodiments show a same configuration or function, and description thereof will be omitted.

A negative pressure generating device of the present embodiment includes an intake recirculation passage 39, a flow rate control device 91 that adjusts the flow rate of the intake air circulating through the intake recirculation passage 39, and an ejector 92 that generates negative pressure in the second blow-by gas reduction passage 37.

As described above, in the negative pressure generating device of the present embodiment, the intake recirculation passage 39 is arranged so as to return the intake air from the second intake passage 32 to the first intake passage 31. Therefore, when the intake compressor starts supercharging and the pressure of the second intake passage 32 becomes positive pressure, a part of the intake air recirculates to the first intake passage 31 through the intake recirculation passage 39. The negative pressure can be generated in the second blow-by gas reduction passage 37 by the ejector 92. At this time, the magnitude of the generated negative pressure can be set optionally and the intake air amount of the engine E and the rotational speed of the turbocharger T can be controlled by the flow rate control device 91.

Therefore, similarly to the second embodiment, in both cases of the supercharging and the natural intake of the engine E, the blow-by gas generated in the crankcase 8 can be recirculated to the intake passage of the engine E. The fresh air passed through the air cleaner 4 can be introduced into the crankcase 8 to ventilate the crank chamber 25.

As described above, the oil cooling system for a supercharged engine of the present embodiment exerts effects similar to those of the first and second embodiments.

Fourth Embodiment

FIG. 8 to FIG. 10 show an oil cooling system for a supercharged engine according to a fourth embodiment.

The reference signs same as those of the first to third embodiments show the same configuration or function, and description thereof will be omitted.

The oil cooling system for a supercharged engine of the present embodiment includes the first oil cooler 1, an oil mist separator 3 disposed downstream of the first oil cooler 1, an lubricating oil supply passage including the first oil supply passage 59, an oil discharge passage including the first and second oil discharge passages 61, 62, a coolant supply passage including the third coolant supply passage 73, and a coolant discharge passage including the third coolant discharge passage 76.

The first oil cooler 1 includes the inner pipe 81 defining the oil cooling passage 68, and the outer pipe 82 defining the coolant circulation passage 78 between the outer periphery of the inner pipe 81 and the outer pipe.

At the upstream end of the inner pipe 81, the oil introduction pipe is arranged which introduces the lubricating oil from the first oil discharge passage 61 into the oil cooling passage 68. Also, at the downstream end of the inner pipe 81, the oil lead-out pipe is arranged which leads out the oil from the oil cooling passage 68 to the second oil discharge passage 62. Further, inner fins improving the heat exchange performance may be installed inside the oil cooling passage 68.

At the upstream end of the outer pipe 82, the coolant introduction pipe 77 is arranged which introduces the coolant from the third coolant supply passage 73 into the coolant circulation passage 78. Also, at the downstream end of the outer pipe 82, a coolant lead-out pipe 79 is arranged which leads out the coolant from the coolant circulation passage 78 to the upper head tank of the radiator 57 through the third coolant discharge passage 76 and the first coolant discharge passage 74. Further, inner fins improving the heat exchange performance may be installed inside the coolant circulation passage 78.

Also, the first oil cooler 1 is configured to cool the lubricating oil utilizing the coolant by a convectional flow in which the lubricating oil flows from one side to the other side of the oil cooler 1, and the coolant flows from the other side to one side of the oil cooler 1.

Even when the oil mist separator 3 is installed in the middle of the second oil discharge passage 62 as shown in FIG. 8, its effect is exerted. In this case, the oil mist particle size enlarging effect in the inside of the crankcase 8 of the engine E shown in the graph of FIG. 9 can be utilized in addition to the effect of the oil mist filter 83 and the plurality of first and second collision plates 84 (refer to FIG. 3A, FIG. 3B, FIG. 4A and FIG. 4B) similar to the first embodiment. The graph of FIG. 9 shows that the particle size of the oil mist is enlarged after the oil mist passes through the connecting passage 26. It is considered that the oil mist with small particle size is adsorbed by the oil mist with comparatively large particle size that scatters in the connecting passage 26.

By connecting the second oil discharge passage 62 to the chain case 10 of the engine E as shown in FIG. 10, the particle size of the oil mist generated in the turbocharger T is enlarged, the surface area of the oil mist is reduced, the oil mist returns to the chain case 10, and the oil-deterioration-suppressing effect can be secured without increasing the number of the components and the cost.

As described above, the oil cooling system for a supercharged engine of the present embodiment exerts effects similar to those of the first to third embodiments.

Fifth Embodiment

FIG. 11 shows an oil cooling system for a supercharged engine according to a fifth embodiment.

The oil cooling system for a supercharged engine of the present embodiment includes the first oil cooler 1, an oil supply passage including the first oil supply passage 59, an oil discharge passage including the first and second oil discharge passages 61, 62, a coolant supply passage including the third coolant supply passage 73, and a coolant discharge passage including the third coolant discharge passage 76.

The turbocharger T includes the intake impellor 41, the housing 42, the exhaust turbine (the impellor 43, the housing 44, the shaft 45), and the center housing 46 installed between the housings 42, 44.

The water jackets W1, W2 are formed in the housing 44 and the center housing 46. In FIG. 11, the water jacket W1 is not shown.

By the center housing 46, two bearings 47 are supported respectively. In this center housing 46, an oil supply section is arranged which supplies the lubricating oil from the oil pump 55 to the bearing storage chamber 48. This oil supply section has the oil pouring port 51, the oil introduction passage 52, the oil distribution passage 53, the oil discharge port 54 and the like.

The oil cooler 1 includes the oil cooling passage 68 through which the lubricating oil from the first oil discharge passage 61 circulates, and the coolant circulation passage 78 through which the coolant of a low temperature from the third coolant supply passage 73 circulates. The oil cooler 1 heat-exchanges the lubricating oil that flows the oil cooling passage 68 with the coolant that flows through the coolant circulation passage 78, so that the lubricating oil is cooled.

At the upstream end of the oil cooling passage 68, an oil introduction section is arranged which introduces the lubricating oil from the first oil discharge passage 61 into the oil cooling passage 68. Also, at the downstream end of the oil cooling passage 68, an oil lead-out section is arranged which leads out the lubricating oil from the oil cooling passage 68 to the second oil discharge passage 62.

Further, in the first oil cooler 1, the oil cooling passage 68 is defined by a U-shaped heat transfer pipe 93. Thus, the lubricating oil after lubricating supercharger stays inside a U-shape section 94 of the oil cooling passage 68, and therefore a liquid seal section 95 is formed. Because the bearing storage chamber 48 and the first oil discharge passage 61 are shut off from the crank chamber 25 of the crankcase 8 by the liquid seal section 95, it can be avoided that the fresh air introduced to the crankcase 8 enters the bearing storage chamber 48 and the lubricating oil after lubricating supercharger is oxidized and deteriorated in the bearing storage chamber 48.

Also, because it takes time for the lubricating oil staying inside the U-shape section 94 of the oil cooling passage 68 before flowing out again from the downstream side of the liquid seal section 95, the lubricating oil is cooled during that time, and the temperature of the lubricating oil can be further lowered. Further, because the oil mist generated in the turbocharger T can be also trapped by the liquid seal section 95, the liquid seal section 95 also has the function of the oil mist separator 3 of the fourth embodiment.

As described above, the oil cooling system for a supercharged engine of the present embodiment exerts effects similar to those of the first to fourth embodiments.

Sixth Embodiment

FIG. 12 shows an oil cooling system for a supercharged engine according to a sixth embodiment.

In the oil cooling system for a supercharged engine of the present embodiment, the downstream side end of the oil cooling passage 68 and the second oil discharge passage 62 of the first oil cooler 1 are connected to each other on the level lower than the oil surface (liquid surface level) of the oil stored in the oil pan 9 in the vertical direction (gravitational direction). Thus, because a liquid seal section 96 that shuts off the bearing storage chamber 48 and the first oil discharge passage 61 from the crank chamber 25 is formed in the oil cooling passage 68 and the second oil discharge passage 62, the effects of the fifth embodiment described above can be secured. This liquid seal section 96 has also the function of the oil mist separator 2 of the first embodiment.

Further, because the lubricating oil after lubricating supercharger is mixed directly with the lubricating oil stored in the oil storage chamber of the oil pan 9, the lubricating oil after lubricating supercharger is not exposed to the fresh air in the crank chamber 25 of the crankcase 8, and the oil temperature of the lubricating oil after lubricating supercharger is equalized and lowered. As a result, a higher oil-deterioration-suppressing effect can be secured.

More specifically, the temperature of the lubricating oil inside the oil cooling passage 68 and the second oil discharge passage 62 can be lowered to the vicinity of the oil temperature or to the same oil temperature of the oil inside the oil storage chamber of the oil pan 9.

As described above, the oil cooling system for a supercharged engine of the present embodiment exerts effects similar to those of the first to fifth embodiments.

Seventh Embodiment

FIG. 13 shows an oil cooling system for a supercharged engine according to a seventh embodiment.

In addition to the configuration of FIG. 10 of the fourth embodiment, the oil cooling system is applied to an engine E having a first partition wall 97 and a second partition wall 98. The oil cooling system has an oil supply passage including the first oil supply passage 59, an oil discharge passage including the first and second oil discharge passages 61, 62, a coolant supply passage including the third coolant supply passage 73, and a coolant discharge passage including the third coolant discharge passage 76.

The first partition wall 97 partitions the internal space of the engine E into the inside of the chain case 10 and the valve gear chamber 27 so that the inside of the chain case 10 and the valve gear chamber 27 do not communicate with each other. The upper end of this first partition wall 97 is hermetically in contact with the ceiling wall surface of the head cover 7, and the lower end is hermetically in contact with the upper end surface of the cylinder head 6.

The second partition wall 98 partitions the internal space of the engine E into the inside of the chain case 10 and the inside (the crank chamber 25) of the crankcase 8 so that the inside of the chain case 10 and the inside of the crankcase 8 do not communicate with each other.

Further, a lower end 99 of the second partition wall 98 is disposed at a position below the oil surface (liquid surface level) of the lubricating oil stored in the oil storage chamber of the oil pan 9 in the vehicle vertical direction (gravitational direction), which is a position lower than the oil surface (liquid surface level) of the lubricating oil and above the bottom surface of the oil pan 9 in the vehicle vertical direction (gravitational direction). Thus, the gap between the lower end 99 of the second partition wall 98 and the bottom surface of the oil pan 9 opens, and the oil storage chamber on the left side in the drawing of the second partition wall 98 and the oil storage chamber on the right side (crank chamber side) in the drawing of the second partition wall 98 communicate with each other.

Also, the engine E includes a liquid seal section 100 that shuts off the communication state between the crank chamber 25 of the crankcase 8, the valve gear chamber 27 and the inside of the chain case 10 by the lubricating oil inside the oil pan 9. This liquid seal section 100 functions also as the oil mist separator 3 of the fourth embodiment.

With the configuration described above, the liquid seal section 100 is formed which shuts off the inside (the crank chamber 25) of the crankcase 8 and the valve gear chamber 27 from the inside of the chain case 10 by the lubricating oil stored inside the oil storage chamber of the oil pan 9, and oxidation and deterioration of the lubricating oil caused as the fresh air introduced to the inside of the crankcase 8 enters the bearing storage chamber 48 can be prevented. As a result, an oil-deterioration-suppressing effect can be secured.

As described above, the oil cooling system for a supercharged engine of the present embodiment exerts effects similar to those of the first to sixth embodiments.

Modified Embodiment

As the supercharger, a turbocharger (turbo supercharger) of an electric type (assist supercharge type), which drives the exhaust turbine and the intake compressor by utilizing the drive force of the electric motor, may be used. Further, as the supercharger, an electric type intake compressor and an engine drive type supercharger (mechanical supercharger) also may be used.

As the lubricating oil cooling device, a multi-plate layered type may be employed. Also, in the oil cooling passage formed between adjacent two metal formed plates, offset type corrugated fins may be inserted and arranged.

Further, it is also possible to employ an lubricating oil cooler that cools the lubricating oil by utilizing the coolant with parallel flows in which the lubricating oil and the coolant flow from one side to the other side of the lubricating oil after lubricating supercharger cooler.

As the oil mist separator 2, 3, a cyclone separator, which generates a swirl flow in the inside and separates the liquid component and the gas component from the oil mist by centrifugal separation, may be employed.

It is also possible to employ a timing belt and belt pulleys which drive and connect the crankshaft 16 and the intake and exhaust cam shafts 21, 23. In this case, the chain cover becomes a belt cover or an engine cover.

It is also possible to store (accommodate) an intake valve gear mechanism that variably changes the valve timing of the intake valve 18 or an exhaust valve gear mechanism that variably changes the valve timing of the exhaust valve 19 in the inside of the valve gear chamber 27. Further, not only a direct drive type but also a locker arm type valve gear mechanism may be employed.

The oil cooler 1 may be connected to the downstream side in the flow direction of the coolant of the radiator such as a heat exchanger for heating (heat core) that heats air supplied into a cabin of the vehicle by the heat of the coolant.

It is also possible to arrange two first and second intake ports which are independently connected to one cylinder in the cylinder head of the internal combustion engine, and to install two first and second intake valves opening/closing the first and second intake port openings at the combustion chamber side end of these first and second intake ports.

In this case, on the intake cam shaft 21, one or two intake cams, which determine the opening/closing timing (valve timing) of the two first and second intake valves, are arranged.

It is also possible to arrange two first and second exhaust ports which are independently connected to one cylinder in the cylinder head of the internal combustion engine, and to install two first and second exhaust valves opening/closing the first and second exhaust port openings at the combustion chamber side end of these first and second exhaust ports.

In this case, on the exhaust cam shaft 23, one or two exhaust cams, which determine the opening/closing timing (valve timing) of the two first and second exhaust valves, are arranged. 

What is claimed is:
 1. An oil cooling system for a supercharged engine in which a supercharger is mounted on an internal combustion engine, comprising: an oil supply passage that supplies lubricating oil to the supercharger; an oil discharge passage that returns the lubricating oil which has lubricated the supercharger to the inside of the internal combustion engine; an oil cooling device that is installed in the oil discharge passage and cools the lubricating oil which has lubricated the supercharger by utilizing coolant; a first coolant passage that supplies coolant at least to the supercharger; and a second coolant passage that branches from the first coolant passage on the upstream side of the supercharger in the flow direction of the coolant, and supplies the coolant to the oil cooling device.
 2. The oil cooling system for a supercharged engine according to claim 1, wherein the oil discharge passage comprises a first oil discharge passage that leads lubricating oil which has lubricated the supercharger to the oil cooling device, and a second oil discharge passage that leads the lubricating oil having been cooled in the inside of the oil cooling device to the inside of an oil pan formed in a crankcase of the internal combustion engine.
 3. The oil cooling system for a supercharged engine according to claim 1, further comprising: a first intake passage that supplies intake air having passed through an air cleaner of the internal combustion engine to the supercharger; a second intake passage that supplies the intake air having been compressed by the supercharger to a throttle valve of the internal combustion engine; a third intake passage that supplies the intake air of which flow rate has been adjusted by the throttle valve to cylinders of the internal combustion engine; a fresh air introduction passage that branches from the first intake passage and connects the air cleaner and a valve gear chamber of the internal combustion engine to each other; a first blow-by gas reduction passage that connects the crankcase and the third intake passage; a check valve that is arranged in the blow-by gas reduction passage and prevents back flow of blow-by gas that flows from the third intake passage to the crankcase; a second blow-by gas reduction passage that connects is connected from any position communicating with the inside of the crankcase to the first intake passage on the downstream side of a branch position of the fresh air introduction passage; and a negative pressure generating device that is installed in the second blow-by gas reduction passage and generates negative pressure in the second blow-by gas reduction passage.
 4. The oil cooling system for a supercharged engine according to claim 3, wherein, the negative pressure generating device comprises: an intake reduction passage that branches from the second intake passage is connected to the first intake passage for returning the intake air from the downstream side to the upstream side of the supercharger; a flow rate control device that adjusts the flow rate of intake air circulating through the intake reduction passage; and an ejector that generates negative pressure in the second blow-by gas reduction passage.
 5. The oil cooling system for a supercharged engine according to claim 1, wherein the first coolant passage has a first coolant supply passage that supplies coolant to the internal combustion engine and a second coolant supply passage that branches from the first coolant supply passage and supplies the coolant to the supercharger; and the second coolant passage has a third coolant supply passage that branches from the first coolant supply passage.
 6. The oil cooling system for a supercharged engine according to claim 1, wherein the oil cooling device has an oil cooling passage which is connected to the oil discharge passage and through which lubricating oil cooled by utilizing coolant introduced from the third coolant passage circulates, and an oil mist separator that captures oil mist in the oil cooling passage.
 7. The oil cooling system for a supercharged engine according to claim 6, wherein the oil mist separator has collision plates that project to the inside of the oil cooling passage so as to be thermally in contact with lubricating oil which has lubricated the supercharger.
 8. The oil cooling system for a supercharged engine according to claim 6, wherein the oil mist separator has a coolant circulation passage through which the coolant cooling the lubricating oil circulating through the oil cooling passage circulates, and collision plates that project to the inside of the coolant circulation passage so as to be thermally in contact with the coolant circulating through the coolant circulation passage.
 9. The oil cooling system for a supercharged engine according to claim 6, wherein the oil cooling device has an oil cooling passage which is connected to the oil discharge passage and through which lubricating oil cooled by utilizing coolant introduced from the third coolant passage circulates; the oil discharge passage has a first oil discharge passage that leads lubricating oil having which has lubricated the supercharger into the oil cooling device, and a second oil discharge passage that leads the lubricating oil which has been cooled in the oil cooling device into an oil pan formed in a crankcase of the internal combustion engine; and the engine has a liquid seal section that is arranged in at least one passage out of the oil cooling passage, the first oil discharge passage, and the second oil discharge passage and shuts off the communicating state between the supercharger and the inside of the crankcase by lubricating oil staying in the middle of the at least one passage.
 10. The oil cooling system for a supercharged engine according to claim 9, wherein the liquid seal section is arranged with at least one passage out of the oil cooling passage, the first oil discharge passage, and the second oil discharge passage being U-shaped.
 11. The oil cooling system for a supercharged engine according to claim 10, wherein the liquid seal section is arranged with the downstream end of the second oil discharge passage being connected to a position below the liquid surface of lubricating oil stored inside the oil pan.
 12. The oil cooling system for a supercharged engine according to claim 1, wherein the oil discharge passage has a first oil discharge passage that leads lubricating oil having lubricated the supercharger into the oil cooling device, a second oil discharge passage that leads the lubricating oil having been cooled in the inside of the oil cooling device into an oil pan formed in a crankcase of the internal combustion engine, and an oil mist separator that is installed in the second oil discharge passage and captures oil mist in the second oil discharge passage.
 13. The oil cooling system for a supercharged engine according to claim 12, wherein the oil cooling device has an oil cooling passage which is connected to the oil discharge passage and through which lubricating oil cooled by utilizing coolant introduced from the third coolant passage circulates, and an oil mist separator that captures oil mist in the oil cooling passage; and the oil mist separator is configured so that the oil cooling passage or the second oil discharge passage communicates with a chain case of the internal combustion engine.
 14. The oil cooling system for a supercharged engine according to claim 13, wherein the internal combustion engine has a first partition wall that partitions the internal space of the internal combustion engine into the chain case and the valve gear chamber, and a second partition wall that partitions the internal space of the internal combustion engine into the crankcase and the chain case; the second partition wall has a lower end at a position below the liquid surface of lubricating oil in the oil pan; and the internal combustion engine has a liquid seal section that shuts off the communicating state between the crankcase and the chain case by lubricating oil in the oil pan. 